Do you ever notice that some rooms in your house are constantly warmer or cooler than all the rest? Adjusting the thermostat up or down won't solve the problem and opening windows can be wasting energy. Consider air balancing your home.
An HVAC (Heating, Ventilation, and Air Conditioning) professional well test the air flow of the central air system to each room of the house. A hood will be placed over each vent to measure the amount volumetric air flowrate. Next, the pressure, humidity, and temperature will be measured. Using some thermodynamic charts and calculations a recommendation for the duct work will be produced.
It can be expensive to fix the imbalance and may only be worth it if the central air in your house is more than 30% off equilibrium. You'll need to weigh the cost of the repairs versus the amount of electricity that will be saved through energy efficiency. The added comfort level should also be considered along side the financial aspect.
Another solution, if the cost of air balancing is too much, is to consider a space heater. Space heaters are excellent at heating small areas and rooms. Set the thermostat to where the hottest room in the house is comfortable and then use the space heater(s) in any room that is needing a little boost in temperature.